638 SUMMAEY OF CUBRENT RESEARCHES RELATING TO 



with granular contents, some of which may be seen to be connected 

 with nerves, while others are lost in the surrounding tissue ; these 

 cells agree in character with those which are to be found in the supra- 

 oesophageal ganglion. The ferment-cells of the liver form vesicles 

 containing brown ferment-spheres, and the ferment itself is digested 

 in acid, neutral, or alkaline solutions. The liver-cells excrete small 

 vesicles which have yellowish contents, and which are evacuated with 

 the ffeces. The calcareous cells are distinguished by the presence of 

 refractive spherules formed of phosphate of calcium. During the 

 summer phosphate of calcium is stored up in the liver, and carbonate 

 of calcium in the walls of the vessels and other regions of connective 

 tissue ; in winter this is used by Helix to form the winter operculum, 

 and in A^-ion, probably, as a means for strengthening the integuments. 

 It is also used by Helix to repair the shell, and by Avion to replace 

 the excreted calcareous dermal mucus. All the constituents found 

 in the liver are always found in the same relative proportions, so that 

 though the absolute weight of the ash varies, the percentage of its 

 constituents is always the same. We see, therefore, that the liver 

 of the Gastropod performs a number of functions which, in higher 

 animals, are undertaken by various separate organs. 



For the purposes of his microscopical investigations Dr. Barfurth 

 places a small piece of liver for ten minutes in a 1 per cent, solution 

 of osmic acid, and then makes sections. 



Sensory Organs of Gastropoda.* — P. B. Sarasin describes the 

 tentacular ganglion of the fresh-water Pulmonata, and finds, as in 

 higher animals, that in the young the nervous system is proportionately 

 better develoj)ed than in the adult ; at first the two tentacular ganglia 

 are placed quite close to the cerebral, and they appear to arise from 

 the sensory plate. 



The so-called organ of Semper is an organ consisting of several 

 lobules, which lies round the mouth, and is richly provided with 

 nerves. In Helix pomatia Sarasin finds that the outer edge of the 

 lobule is covered by a strong cuticle, beneath which there is an epi- 

 thelial layer of elongated and a mass of ganglionic cells ; connected 

 with this nervous mass is a well-developed nerve, and the whole 

 structure calls to mind the arrangement of a tentacular ganglion ; both 

 these organs are absent from the Prosobranchiata. 



The olfactory ganglion has been examined in a number of species, 

 and the cells which compose it have been found to be large and very 

 distinct, though in the Stylommatophora it is, as compared with the 

 Basommatophora, in a rudimentary condition. 



The author concludes with some observations on the glands of the 

 foot, and states his conviction that the Basommatophora and Stylom- 

 matophora have many points in common. 



Pedal Nerves of Haliotis.t — H. Wegmann, bearing in mind the 

 opposing statements of Lacaze-Duthiers and Spengel, finds that, in 



* Arbeit. Zool.-Zoot. Inst, Wurzburg, vi. (1883) pp. 91-108 (1 pi.)- 

 t Comptes Rendus, xcvii. (1883) pp. 274-6, 



